Note - History of the Atomic Theory
o 400 BC: Empedocles
 Matter is composed of 4 elements: _____
o 400 BC: Democritus
 All matter was made of tiny particles:_____
o 500 - 1600 AD
 Alchemists: tried to make gold from cheap metals
 Devised first chemical symbols
o 1808: John Dalton’s atomic model
1. All matter is made of atoms, which are _________________
2. Each element has its own kind of _______.
3. Compounds are created when atoms of different elements ______
4. Atoms cannot be ________
Dalton atom - 1808:
•
•
•
J.J. Thomson’s atom: 1904
Uniform ___
No ____ particles
•
•
•
Uniform, ___ density sphere
Small, ____ embedded in a positive
matrix
Similar to a soft ________
Rutherford Atom
•
Low density sphere, with ____
•
Centre is ___ charged
•
•
Outer region contains negatively
charged ___.
He devised this theory via his
famous _____
Atomic Structure
 All matter is made of tiny particles called ….
 Each atom is made of 3 types of smaller
particles:
Symbol
Charge
Location in
Atom
…
Nucleus
…
Mass number = (#... ) + (#...)
Example: carbon-12 has:
Mass # =
=
Atomic Symbols:
tell us the
23
11Na
Example 1:
type of atom = …
# protons/atomic # =
Mass # =
- Mass number =
- Atomic number = Number of Protons =
- If mass # = , and # protons =,
# neutrons =
=
Example 2:
35
17Cl
For a chlorine atom with symbol,
find:
a)
b)
c)
d)
Mass Number
Atomic Number
# protons
# neutrons
a)
mass number =
b)
Atomic Number =
c)
# protons =
d)
# neutrons =
Example 3: For a uranium atom with symbol,
238
92U find:
a)
b)
c)
d)
mass number
Atomic #
# protons
# neutrons
a)
mass number =
b)
Atomic # =
c)
# protons =
d)
# neutrons =